In the course of a free expansion process___________________?
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Answer: C. both A. and B. above
Explanation
Free expansion occurs when a fluid expands into an evacuated chamber without overcoming any external resistance. Because no boundary moves against an external force, the work done during free expansion is zero. Assuming the container is thermally insulated, no heat is transferred, satisfying both conditions. Joule expansion experiment famously demonstrated that free expansion of an ideal gas causes zero temperature change. The process is highly irreversible and generates entropy due to unrestrained fluid turbulence. First law energy balance confirms that internal energy remains constant for ideal gases during free expansion.
Pneumatic systems experiencing sudden vessel rupture or burst disc failures undergo rapid free expansion. Cryogenic storage vessel safety relief systems must be evaluated for sudden gas expansion effects. Teaching free expansion helps students understand the difference between reversible and irreversible work. Stating only that work done is zero misses the crucial simultaneous absence of heat transfer. Claiming only zero heat transfer ignores the equally important zero work condition during vessel expansion. Increasing or decreasing heat during free expansion contradicts the standard adiabatic test setup conditions.
- Subject
- Engineering
- Category
- Mechanical Engineering
- Topic
- —
- Difficulty
- medium
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